Ezio Mancaruso

Study of the multi-injection combustion process in a transparent direct injection common rail diesel engine by means of optical techniques

Abstract A combination of ultraviolet—visible optical diagnostics has been applied in the combustion chamber of a diesel engine in order to study the fuel injection, autoignition, and soot formation processes. Measurements were made in an optically accessible diesel engine equipped with a multivalve cylinder head and a common rail (CR) high-pressure injection system. Several multi-injection strategies, characteristic of new generation CR diesel engines, were tested. They consisted of two (pre + main) and three (pre + main + post) injections per cycle. Fuel injection and visible combustion were studied by imaging the natural flame luminosity, and soot formation and evolution were evaluated by means of the two-colour pyrometry method. The reactions that occur during autoignition and soot formation were investigated by chemiluminescence imaging, while the broadband ultraviolet—visible extinction and scattering spectroscopy (BUVESS) technique was used in order to measure the soot particle size and number concentration. For all the injection strategies investigated, pre injection has contributed to the reduction of the ignition delay of the main injection. Moreover, the present study showed that autoignition can be characterized to some degree by the presence of the OH radical. The effect of post injection on combustion development and soot particle diameter has also been observed and discussed.

Multiwavelength ultraviolet absorption spectroscopy of NO and OH radical concentration applied to a high-swirl diesel-like system

Ultraviolet absorption measurements were carried out in an optical research engine by exploiting the emitted plasma kernel of laser-induced breakdown. Temporal evolution and spatial distribution of OH radical and NO absolute concentrations were evaluated by a numerical procedure for retrieving optical data. Spectral measurements were made in an optically accessible external combustion chamber obtained by modifying a single cylinder, four-stroke diesel engine. The experiments were performed using a commercial diesel fuel at two engine speeds varying the ignition delay and fixing the injected fuel amount. In-chamber NO concentrations for each engine operating condition were correlated with those measured at the exhaust by a conventional method.

Investigation of the combustion in both metal and optical diesel engines using high-glycerol ethers/diesel blends

In this article, a glycerol ethers mixture obtained from etherification of glycerol with tert-butyl alcohol and isobutylene has been used in blend (10% and 20% v/v) within a commercial diesel fuel to feed a single-cylinder research engine derived from a Euro5 compliant four-cylinder engine. The engine has been run in three significant operating points in the New European Driving Cycle emission homologation area. The results have shown the possibility to burn the diesel–glycerol ethers mixture blends without significant impact on combustion characteristics and efficiencies while, due to the oxygen content of the glycerol ethers mixture, important benefits are obtained in terms of NOx-particulate matter trade-offs at the exhaust. Moreover, tests have been performed on a diesel engine with optical access through the piston bowl. The injection and combustion processes of the pilot have been investigated by means of the simultaneous use of digital imaging in the visible and infrared ranges in order to have more information on the vapour distribution, the fuel motion before the ignition and the location of hot gas.

ANN-based Virtual Sensor for On-line Prediction of In-cylinder Pressure in a Diesel Engine

Abstract This study presents the process design and tune-up of robust artificial neural networks (ANN) to be used as virtual sensors for the diagnosis of a three-cylinder Diesel engine operating at various conditions. Particularly, a feed-forward neural network based on radial basis functions (RBF) is employed. The use of different radial basis functions, and their relevant parameters, is investigated in detail, with their effect on the network accuracy. The RBF network is validated using data not included in training, showing good correspondence between measured and reconstructed pressure signal. The accuracy of the predicted pressure signals is analyzed in terms of mean square error and in terms of a number of pressure-derived parameters. Results are promising in terms of performance and accuracy, both for the predicted pressure signals and for the pressure-derived engine parameters that can be used in a closed loop engine control system.

Assessment of a New Quasi-Dimensional Multizone Combustion Model for the Spray and Soot Formation Analysis in an Optical Single Cylinder Diesel Engine

An innovative quasi-dimensional multizone combustion model for the spray formation, combustion and emission formation analysis in DI diesel engines was assessed and applied to an optical single cylinder engine. The model, which has been recently presented by the authors, integrates a predictive non stationary 1D spray model developed by the Sandia National Laboratory, with a diagnostic multizone thermodynamic model. The 1D spray model is capable of predicting the equivalence ratio of the fuel during the mixing process, as well as the spray penetration. The multizone approach is based on the application of the mass and energy conservation laws to several homogeneous zones identified in the combustion chamber. A specific submodel is also implemented to simulate the dilution of the burned gases. Soot formation is modeled by an expression which derives from Kitamura et al.s results, in which an explicit dependence on the local equivalence ratio is considered. The model was used to analyze low load (BMEP = 2 bar at 1500 rpm) and medium load (BMEP = 5 bar at 2000 rpm) operating conditions in an optical single cylinder engine sharing the combustion system configuration of the 2.0L Euro5 GM diesel engine for passenger car application.

A comprehensive analysis of the impact of biofuels on the performance and emissions from compression and spark-ignition engines:

The compression ignition and small displacement spark-ignition engines play an important role in the urban air pollution. In particular, vehicles equipped with compression ignition engines are widely used because of their higher performance and fuel efficiency with respect to the spark-ignition ones. Nevertheless, spark-ignition engines with low displacements are even more wide-spreading because of the lower fuel consumption and emissions. They are also used for two-wheeled vehicles, whose easier navigation makes them widely used in heavily congested areas. Their contribution on urban pollution is worsened by the fact that these vehicles have to comply with the Euro 3 standard; light vehicles have, instead, to fulfill the more restrictive Euro 6, which for the compression ignition and gasoline direct injection engines indicates for particle emissions also a number-based regulation. This article aims to characterize the effects of biofuels on engine emissions and performance of compression ignition and spark-ignition engines. The investigation was carried out on different class of engines. Direct injection and a port fuel injection spark-ignition engines fueled with ethanol and its blends, 10 v/v%, 50 v/v% and 85 v/v% of ethanol in gasoline. The compression ignition engine was equipped with a common rail injection system and was fueled with pure rapeseed methyl ester, representative of fatty acid methyl ester, and its blends in diesel, 20 v/v% and 50 v/v%. The gaseous emissions and the particle concentration were measured at the exhaust by means of conventional instruments. Particle size distribution function was measured in the range from 5.6 to 560 nm by means of an engine exhaust particle sizer. A comprehensive characterization of the particulate carbon was performed by means of optical diagnostics in the combustion chamber. In particular, two-dimensional images of flame evolution were detected and processed by two-color pyrometry technique to assess the in-cylinder soot formation and oxidation processes. For both the investigated spark-ignition and compression ignition engines, the use of biofuels shows a partial increase in the specific fuel consumption and a reduction of the soot particles emission. Nevertheless, a further effort on engine technology should be paid to balance the mass with the size and number of the particles.

Characterization of Soot Particles Produced in a Transparent Research CR DI Diesel Engine Operating with Conventional and Advanced Combustion Strategies

The effect of the combustion mode on particle emission was analyzed both in the cylinder and at the exhaust of a direct injection (DI) Common Rail (CR) transparent research diesel engine by means of spectroscopic and conventional methods. The engine was equipped with a flexible electronic control unit (ECU) capable of operating up to 5 injections per cycle with different start of injection and dwell time allowing performing different combustion modes. The conventional diesel combustion, the homogeneous charge compression ignition (HCCI), and the low temperature combustion (LTC) modes were analyzed. In-cylinder broadband UV–visible scattering and extinction measurements were carried out to follow the particle formation and oxidation processes as well as to have information about their chemical nature and size distribution. The characterization of the particulate emission at the exhaust was performed by means of an electrical low pressure impactor (ELPI), for the counting and the sizing of the particles, and an opacimeter, for measuring the smoke opacity. The in-cylinder measurements highlighted that particles ranged from 3 to 100 nm whatever was the combustion mode. Nevertheless, particles produced by a conventional diesel combustion process principally consist of soot. Whereas particles formed during HCCI and LTC modes are composed mainly of organic compounds. The exhaust particle emissions depend on the combustion mode both in terms of size and number. A larger amount of particles smaller than 100 nm was emitted during HCCI and LTC modes with respect to the conventional one. Moreover, HCCI mode showed a strong accumulation mode. Copyright 2012 American Association for Aerosol Research

Spray and Soot Formation Analysis by Means of a Quasi-Dimensional Multizone Model in a Single Cylinder Diesel Engine under Euro 4 Operating Conditions

An investigation has been carried out on the spray penetration and soot formation processes in a research diesel engine by means of a quasi-dimensional multizone combustion model. The model integrates a predictive non stationary 1D spray model developed by the Sandia National Laboratory, with a diagnostic multizone thermodynamic model, and is capable of predicting the spray formation, combustion and soot formation processes in the combustion chamber. The multizone model was used to analyze three operating conditions, i.e., a zero load point (BMEP = 0 bar at 1000 rpm), a medium load point (BMEP = 5 bar at 2000 rpm) and a medium-high load point (BMEP = 10 bar at 2000 rpm). These conditions were experimentally tested in an optical single cylinder engine with the combustion system configuration of a 2.0L Euro4 GM diesel engine for passenger car applications. The experimental spray tip penetration and spreading angle were evaluated on the basis of images acquired by means of a high-speed CCD camera, while the experimental trend of the in-cylinder soot concentration was derived by means of the two-color pyrometry method. The acquired experimental data have allowed useful information to be obtained for the assessment of the multizone model. Well-defined trends between some of the model parameters and the engine operating conditions (namely, speed and load) have been found and preliminary correlations have been developed

Use of in-Cylinder Pressure and Learning Circuits for Engine Modeling and Control

The parameter widely considered as the most important for the diagnosis of combustion process in internal combustion engines is the cylinder pressure and numerous control algorithms based on pressure measurement as a feedback signal have been proposed. Use of real-time cylinder pressure in control architectures for both SI and Diesel engines allows to replace many other sensors present in engines and offers a variety of significant advantages in terms of improved engine performances and reduced toxic emissions. The present chapter provides an overview of the main applications of cylinder pressure signal analysis in engine modeling and control.

Non-interfering Diagnostics for the Study of Thermo-Fluid Dynamic Processes

The conversion of chemical energy into mechanical power, operated by internal combustion engines, involves a great number of complex phenomena that often occur in transient thermo-fluid dynamic conditions. The majority of these phenomena are affected by nonlinear dynamics, thus requiring appropriate compensation techniques. The analysis and comprehension of these nonlinear processes is a basic requirement for the design of effective control solutions, able to optimize the combustion processes in terms of engine power, efficiency, and emissions. In this chapter, we present some advanced non-interfering optical diagnostics that allow to study in detail the reasons and the effects of the nonlinear behavior of many processes occurring in internal combustion engines.